17 Bottlebrush Avenue, · MCU26/0001

Catchment

    •   Total area: 505 m² (0.051 ha)

    •   Tc components:

            1.   Roof inlet time Q 5 minutes

                        Assigned based on standard inlet times from QUDM Table 4.6.2 for urban residential
                         areas.

            2.   Time in pipe flow → 2 minutes

                        Pipe length: 10 m

                        Slope: 0.5%

                        Manning's n: 0.012

                        Using Manning’s equation, the travel time is calculated based on hydraulic parameters.

            3.   Total Time of Concentration (Tc): 7 minutes



Calculation Methodology

    •   Roof inlet travel times were estimated using QUDM guidelines and empirical flow path analysis.

    •   Pipe flow times were determined using Manning’s equation for open channel and pipe flow, referencing
        the chart provided in the screenshot for additional validation.

    •   Catchment delineation and flow paths were confirmed using the development layout and area tool
        measurements.



Final Considerations

    •   One catchment has been adopted for the entire development, the development site flows will be conveyed
        to the proposed detention tank.

    •   These times of concentration will be used in hydrological modelling to determine peak flow rates and
        ensure adequate stormwater infrastructure design.




3.3       Hydrological Modelling Results

Analysis of Unmitigated DRAINS Model Results and Required Mitigation Measures

A review of the unmitigated DRAINS model results indicates a significant increase in peak flows across various
AEP storm events due to the transition from an existing low-density residential condition to a more intensive urban
condition.




 17 BOTTLEBRUSH AVENUE, NOOSA HEADS
                                        7 January 2026                                             P a g e | 12
 Stormwater Management Plan
 Client Reference: P0433-25-001
 Prepared for Made Capital PTY LTD